Positron emission tomography (PET) is an important molecular image modality and its application on preclinical research has increased during last decades. Thus, in laboratory practice, it is important to implement a quality control of the equipment, since intrinsic factors influence the image quality. The objective of this work was to perform and implement spatial resolution tests for the small animal PET scanner of the Molecular Imaging Laboratory, LIM/CDTN. Empirically, spatial resolution of a PET scanner can be determined from the measurement of point or linear sources and FWHM (full width half maximum) analysis of the respective linear profiles. In this work, a point source of 22Na and a hot rod style phantom filled with 18F-FDG solution were used. Acquisition and reconstruction of images were performed with the LabPET 1.12.1 software, provided by the equipment manufacturer. Image reconstruction parameters followed the LIM standard protocol: MLEM-3D algorithm, 20 iterations, no high resolution mode, no attenuation or scatter corrections, no post-filtering. PeakFit® and Amide softwares were used to perform images post-processing. The results indicate that the scanner has an adequate spatial resolution and its value is compatible with values reported in international studies performed on similar equipments.

LabPET GE 4 (a small animal positron emission tomograph) image acquisition is done by 1536 independents channels. Differences in the rate counting of each channel must be corrected so as not compromise image quality. Equipment user manual recommends that normalization of the detectors efficiency be made as often as possible and always whenever there are hardware or software parameters changes - included, but not limited to channels parameters adjustments, electronic cards replacements, channels activation or inactivation or software update. This work evaluates the normalization effects on the image quality parameters. PET image acquisition were performed using recommended parameters by the NEMA NU 4-2008 standards. Image was reconstructed in different ways using different normalization files. The tests performed indicated that the image quality parameters do not vary significantly with different normalization data. Therefore, a daily routine of normalizations is not justified, suggesting a periodical frequency of one month or more for this procedure.

Computed Tomography (CT) is a diagnostic imaging method and has been widely used in medical applications. CT exams have increased substantially and promote higher dose deposition in population. CT dosimetry references are characterized by Computed Tomography Dose Index (CTDI). In this work was used a set of two head CT phantoms, made of PMMA. The first head phantom is the standard adult, and it is a cylinder with 16 cm in diameter and 15 cm in length, coupled to a complementary cylinder of PMMA with the same diameter and 7,5 in length. In this phantom set, a circular sheet of GAFCHROMIC® XR-QA2 radiochromic film was loaded between the cylinders. A distance of 10 cm of the phantom set was scanned with the film in the central slice position, using an X-ray beam of 100 kV and 200 mA.s. The scanning was made in a CT scanner GE, LightSpeed VCT model with 64 channel. Digital film images were obtained before and after the CT scanning and they were processed with the digital image viewer imageJ software, to obtain the dose variation in the central slice recorded by the film sheet. Dose variation profile were obtained for horizontal and vertical axes (X and Y) of the central slice. The absorbed dose recorded on the film ranged from 18.03 to 30.40 mGy for the X axis and from 21.52 to 33.85 mGy for the Y axis. The dose value obtained in center, where is the intersection of the X and Y axes, was approximately 22.73 mGy. From these values it became possible to calculate the CTDIvol value using radiochromic films.

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The small animal positron emission tomography (PET) scanner from Molecular Imaging Laboratory (LIM/CDTN) is dedicated to pre-clinical studies on new 18F and 11C-based radiopharmaceuticals and to development of novel applications for well-known radiopharmaceuticals. Thus, quality control tests recommended by the publication NEMA NU 4-2008 are routinely carried out to ensure the proper performance of PET scanner. The aim of this work was to evaluate the influence of image reconstruction protocols on the image quality, accuracy of attenuation and scatter corrections parameters for 18F and 11C PET images. PET images of the image quality phantom filed with 18F-FDG or 11C-PK1122 were acquired and then reconstructed using different reconstruction protocols. The reconstruction variables evaluated were the algorithms (FBP, MLEM-3D, OSEM-3D), the resolution mode (high/standard) and the number of iterations (10 to 150). Uniformity, spill-over ratio (SOR) and recovery coefficients (RC) tests were performed for each reconstructed image according NEMA NU 4-2008. PMOD software was used for image analysis. FBP based protocol generated noisier images compared to iterative algorithms (MLEM-3D or OSEM-3D) based protocols. The increase in the number of iterations resulted in higher standard deviation of the analyzed parameters for all reconstructed images. MLEM-3D and OSEM-3D based protocols generates similar results when number of iterations and resolution mode were identical. SOR and RC mean values remained stable when the number of iterations ranged from 40 to 150. This study allowed the evaluation of different image reconstruction protocols on important parameters of 18F and 11C PET image quality. Additionally, standard image reconstruction protocols to be adopted in LIM/CDTN laboratorial routine for 18F and 11C images reconstruction in preclinical studies were defined.

Os equipamentos utilizados no radiodiagnóstico são amplamente difundidos na sociedade e são importantes para o diagnóstico clínico do indivíduo vivo. Entretanto, também podem contribuir no âmbito jurídico através do emprego das técnicas na radiologia forense, uma área da medicina legal que está em constante evolução. A radiologia forense pode ser subdividida em áreas de crimes violentos, não violentos, ante-mortem ou post-mortem; e possui aplicação desde a inspeção de bagagens, cargas e veículos em regiões de fronteiras, até casos de lesões corporais graves e homicídios. Este trabalho tem por objetivo apresentar uma revisão sistemática da aplicação das modalidades de radiodiagnóstico na ciência forense humana, discutindo a relevância dos procedimentos disponíveis e a atuação do profissional das técnicas radiológicas. A radiologia forense pode incluir a utilização de equipamentos de raios-x, tomografia computadorizada, ressonância magnética e medicina nuclear. As técnicas de radiodiagnóstico aplicadas à ciência forense humana são bem aceitas no meio jurídico e podem auxiliar no esclarecimento de crimes violentos. As imagens devem ser adquiridas por um profissional das técnicas radiológicas e tal função deve estar de acordo com as normas vigentes de radioproteção.

Performance testing of small animal PET scanners is very important to ensure the high performance required for this particular type of PET scanner. In this sense, National Electrical Manufactures Association (NEMA) published its NU 4/2008 standards, a consistent and standardized methodology for measuring scanner performance parameters for small animal PET imaging. Imaging capabilities of the scanner LabPET SOLO 4 were tested during two years according NEMA NU 4/2008 methodology. Results indicates that the equipment, despite a decade of use, presents performance appropriated and similar to performance of equipments reported in Literature.